1. Field of the Invention
The present invention relates to a fuel supply control apparatus for an internal combustion engine, more particularly to a control apparatus capable of adequately controlling the increment of fuel mixture to be supplied so as to compensate the increase of load, which is required of the engine, when auxiliary equipment of a car, such as a car air conditioner, headlights, a power steering device and so on, operates.
2. Description of the Related Art
When an internal combustion engine is burdened with increased load, a number of revolutions of the engine decreases, unless the engine is controlled so as to increase its output power. The number of revolutions is remarkably decreased especially during a time when the output power of an engine is small, as in the idling state thereof. In order to prevent the decrease of a number of revolutions, there has been proposed a control apparatus as disclosed in U.S. patent application Ser. No. 105,913 (filed Oct. 8, 1987 and assigned to the assignee of the present application), for example. According to the prior art described above, when a relatively large load is put on an engine during the idling state thereof, i.e., when a driver turns on a switch for operating a car air conditioner, for example, the control apparatus produces an actuating signal to a by-pass valve for supplying additional air for the engine by by-passing a throttle valve which is closed in the idling state. An actuating signal having a different value is stored in advance in a table within the control apparatus for every kind of load, and it is read out therefrom in response to a load required. Namely, an actuating signal produced by the control apparatus corresponds to a kind of auxiliary equipment required to operate. The opening degree of the by-pass valve is determined accordingly, and additional air is introduced into the engine through the by-pass valve.
After that, an amount of fuel to be increased in response to introduction of the additional air is also retrieved from another table within the control apparatus with the aforesaid actuating signal, and then fuel according to the retrieved amount is supplied for the engine, so that the fuel is increased commensurately with the amount of the additional air. As a result, the output power of the engine is increased and hence the number of revolutions thereof is prevented from decreasing.
The prior art control apparatus as described above has the following drawback. When a switch for requiring auxiliary equipment to operate is turned on, the auxiliary equipment is actuated immediately, but the fuel mixture, the flow rate of which is increased so as to compensate for the increase in load caused by operation of the auxiliary equipment, reaches the engine at a later time. As a result, a number of revolutions of the engine decreases temporarily, and the operational condition of the engine becomes unstable.